Head plate for structural columns



March 29, 1960 e. E. STREHAN 2,930'221 HEAD PLATE FOR STRUCTURAL COLUMNS Original Filed Oct. 20, 1951 HEAD PLATE FOR STRUCTURAL COLUMNS George E. Strehan, Leonia, N.J., assignor to Lally Column (30., Cambridge, Mass., a corporation of Massachusetts Original application October 20, 1951, Serial No. 252,273, now Patent No. 2,768,520, dated October 30, 1956. Divided and this application August 31, 1956, Serial No. 607,385

2 Claims. (CI. 72-15) This invention relates to improvements in headplates or frames for structural columns used in monolithic, fireresistant buildings in which a floor slab of reinforced concrete or the like is poured in place around the supporting columns.

This application is a division of my co-pending application Serial No. 252,273, filed October 20, 1951 and now issued as Patent No. 2,768,520. 7

Channel type head frames designed for this general purpose are disclosed in my Patent No. 2,033,595, dated March 10, 1936, and in the'Donahue and Strehan Patent No. 2,469,455, dated May 10, 1949. In the latter patent, the head frame is rigidly secured to the top of a well known type of prefabricated structural column comprising a steel casing filled with concrete. Such framed columns are adaptable and adequate for all building conditions; they are'easy to install and maintain; they present minimum obstruction to light and air and obviate bulky columns and bulging projections under the panel joints of a flat slab floor; and they afford other practical advantages which are explained in the patents just mentioned.

The principal purpose of the invention is to provide a head frame of relatively simple and economical construction, comprising a pair of fiat steel plates rigidly secured together and, to the ends of upper and lower concretefilled columns, and reinforced by shear and bond rods which are preferably welded to one of the plates and so disposed that portions of the rods may be-bent to most effective position after the upper column is installed and before the concrete slab is poured.

The improved, reinforced head plate serves to transmit to the connected columns that portion of the movement of the rigid frame, based on the relative rigidity of the columns and the intersecting bands of the concrete slabs at the panel joint; and to transmit the total panel load to the column in shear, while reducing the shear in the slab to a small percentage of the ultimate compressive strength of the concrete.

A further object of the invention is to provide a reinforced head plate having projections, preferably formed by portions of the reinforcing rods, on its under side, which serve as ties to prevent cracking or spalling of the concrete in which the plate is embedded; and having rod projections above the plate, which are adequate to resist the horizontal shear in the slab in both directions, thus ensuring the rigidity of a fixed hinge and preventing differential movement between the column head and the floor slab.

Additional advantageous features of the improved head plate will become apparent from the following description of the recommended embodiments of this invention shown on the accompanying drawing, in which:

Fig. 1 is a fragmentary section of a floor slab at the panel joint, showing portions of the assembled upper and lower columns and the head plate in elevation; and

Fig. 2 is a plan view of the head plate.

As shown in the drawings, a flat plate 11, welded to nited States Pate'nt O the top of the lower column 14, is rigidly connected 'by riveting, welding, or other means, as at 13, to a smaller fiat plate 12 which is welded to the lower end of the upper column 15. Four pieces of reinforcing rod are bent in the form of loops 21, having crossed ends with end portions 22. The end portions of each are welded to plate 11 adjacent one of its edges. A number of studs 23 are welded or riveted to the under side of plate 11. Plate 11 and the loops are assembled on to column 14 at the factory, with loops 21 bent out to the general position indicated by the dotted outline 24 in Fig. 1. On the job, after the upper column has been set in place, and plate 12 secured to plate 11, loops 21 are bent to an inwardly inclined position overlying plate 12, and the floor slab is then cast around the head plate assembly.

The composite head plate thus consists of relatively small steel shapes, and is wholly embedded and concealed Within the normal thickness of the concrete floor slab 16. The cross-sectional area of the column head should be such that the total panel load is transmitted to the column in shear; and the lateral dimensions of the head plate should be suflicient to reduce the shear in the slab to ap I proximately three percent of the ultimate compressive strength of the concrete.

The section modulus of the plate should be adequate to transmit that portion of the total negative moment resisted by the columns in proportion to the relative rigidity factors of the columns. The total cross-sectional area of the steel reinforcing rods, above the plate 11, should be adequate to resist the horizontal shear of the slab in both directions.

Although the plates 11 and 12 are preferably square when used as the head frames of interior columns, one or more sides of the plate 11 may be partially cut away for use on exterior columns or in corners. It will also be understood. that the ultimate angular position of the inwardly bent loop portions will depend upon the requirements of the particular installation.

A column head constructed as herein described is easy and economical to fabricate and to assemble with the concrete filled. columns; it affords adequate rigidity,

strength and resistance to shear, and is firmly bonded to the floor slab; and it is compact, relatively light in weight, and convenient to install in meeting the requirements of flat slab building construction.

What is claimed is:

1. A head frame assembly embedded in a concrete slab and connecting two prefabricated structural columns disposed one above the other, comprising: a first fiat head plate attached to the lower column, having a central portion resting on the lower column and overhanging side portions extending outward into the slab around the base of the upper column; a second plate attached to the base of the upper column and mounted directly on the firstv plate, said side portions of said first plate extending outward beyond said second plate, and a plurality of reinforcing rod loops having ends attached to said side portions of the first plate, said loops extending obliquely inward and overhanging the second plate and forming a reinforcing network around the base of the upper coldirectly on said first plate, said side portions of said first plate extending outward beyond said second plate; and a plurality of closed loops of reinforcing rods having ends fixed to said side portions, said loops having bendable Patented Mar 29,1960

1 3 portions which are free of said first plate and extend 1,550,316 obliquely inward and overhang thesecond plate, thereby 1,625,899 forming a reinforcing network around the base of the 2,562,601 upper column. 2,768,520

References Cited in theme of this patent 5 UNITED STATES PATENTS 971,665 Conzelman 0ct.. 4, 1910 4 Hardison Aug. 18, 1925 Lally Apr. 26, 1927 Caquot et a1 July 31, 1951 Strehan Oct. 30, 1956 FOREIGN PATENTS Sweden Oct. 16, 1912 

